Recently, in cellular mobile communication systems, transmission of large-capacity data not only audio data but also still image data, moving image data, and the like is generally performed in accordance with implementation of information in multimedia. In order to implement the transmission of large-capacity data, technologies for realizing a high transmission rate by using a high-frequency wireless band are actively reviewed.
However, when a high-frequency wireless band is used, a high transmission rate can be expected in a short distance. However, as the distance becomes longer, the attenuation according to a transmission distance increases. Accordingly, when a mobile communication system using a high-frequency wireless band is practically operated, the coverage area of a wireless communication base station apparatus (hereinafter, abbreviated as a base station) is decreased. Therefore, more base stations need to be installed. In order to install the base station, corresponding costs occur. Accordingly, technology for realizing communication services using a high-frequency wireless band with an increase in the number of the base stations being suppressed is strongly demanded.
For such a demand, in order to increase the coverage area of each base station, as represented in FIG. 1, relay transmission technologies in which wireless communication relay station apparatuses 1 and 2 (hereinafter, abbreviated as relay stations) are installed between the base station 5 and wireless communication mobile station apparatuses 3 and 4 (hereinafter, abbreviated as mobile stations), and communication between the base station 5 and the mobile stations 3 and 4 is performed through the relay stations 1 and 2 are reviewed. When the relay technology is used, terminals 3 and 4 that cannot directly communicate with the base station 5 can communicate through the relay stations 1 and 2.
As methods of controlling the relay stations and the mobile stations, there are centralized control and autonomous distributed control. The centralized control is a method in which the base station 5 manages all the resources between the relay stations 1 and 2 and the base station 5, between the relay stations 1 and 2 and the mobile stations 3 and 4, and the base station 5 generates control information and controls allocation thereof. The autonomous distributed control is a method in which the relay station 1 manages the resources of the mobile station 3 connected to the relay station 1, the relay station 2 manages the resources of the mobile station 4 connected to the relay station 2, and the relay stations 1 and 2 generate control information and controls the allocation thereof.
The centralized control can flexibly change the amount of allocation in accordance with a change in the traffics of the relay stations 1 and 2. In addition, in the centralized control, cooperative relay that is simultaneously relayed by a plurality of relay stations 1 and 2 can be implemented in an easy manner. On the other hand, in the distributed control, the amount of allocation can be changed in accordance with an instant SINR (Signal-to-Interference plus Noise power Ratio) between the relay stations 1 and 2 and the mobile stations 3 and 4. In addition, the distributed control can decrease the scheduling load of the base station 5. In Non Patent Citation 1, a system in which a system performing centralized control and a system performing distributed control coexist is proposed.
[Non Patent Citation 1] IEEE 802.16 Broadband Wireless Access Working Group IEEE C802. 16j-07/247MS handover in transparent RS and non-transparent RS coexisting multi-hop relay network